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RESULTS



SURVEY CONDITIONS
To fulfill the assessment guidance, information on precipitation (MA DEM 1998, Table B2) and stream discharge (DWM data, Table B3) (Socolow et al. 1999 and 2000, Table B4) were analyzed to estimate hydrological conditions during the water quality sampling events. This review was conducted to estimate the streamflow condition in relation to the 7-day, 10-year (7Q10) low flow. Additionally, this review was used to determine whether the fecal coliform bacteria data were representative of “wet” or “dry weather” sampling conditions.
With the single exception of June 1998, the flows during the sampling events were below average monthly conditions. The June 1998 flows even exceeded the monthly average for the period of record (POR) as reported in Socolow et al. (1999). Flows on the North Nashua River and Nashua River were three times higher than the monthly POR and the Squannacook River was four times higher than the monthly POR. Survey conditions are described below for each DWM sampling event reviewed for the assessment.
USGS Gage 01096500 is located in East Pepperell, MA immediately downstream of a powerplant, which regulates flow. Data from this gage while included in Table B4 is not included in the following survey condition summaries and if used should be interpreted with caution.
27 May 1998: This survey was conducted during and following relatively dry weather (Table B2). Streamflows (Table B4) were below the monthly averages for May 1998 and above the period of record for each USGS streamflow gage (01094400, 01094500, 01096000). Discharges on the North Nashua River were three to six times higher than the 7-day, 10-year (7Q10) low flow estimates (USGS 1998). Similarly the Squannacook River discharge was nine times higher than the low flow estimates (Table B4). Data collected during this survey are interpreted as being representative of dry weather conditions.

17 June 1998: Daily precipitation at the Leominster gage ranged from 0.15 inches on the sampling date to 2.10 inches four days prior to t


he water quality sampling event (Table B2, Figure B4.). Similar precipitation patterns were also recorded at the Kendall Reservoir Station #423 (Table B2). As detailed in Table B4 the flow at the USGS gages responded to the precipitation events. Increases in flow in the North Nashua River are depicted in Figure B4, a and b, and increases in flow in the Squannacook River are depicted in Figure B4, c, with storm event effects reaching the downstream flow gages at progressively later dates. Following the storm event, flows began decreasing, but had not yet reached the monthly average by the sampling date. Discharges on the North Nashua River were approximately 30-66 times higher than the 7-day, 10-year (7Q10) low flow estimates (USGS 1998). The Squannacook River responded similarly with a flow approximately 119 times higher than the low flow estimates (Table B4). The data (interpreted with caution) are considered as being representative of wet weather conditions.
2
Figure B4. Flow and precipitation data for the Nashua River Basin during the period of 6/12/98 through 6/17/98. Flow data from USGS gages. Precipitation data from Leominster station # 517.
1-22 July 1998:
Surveys were conducted during and following relatively dry weather (Table B2). Streamflows were below the monthly averages for July 1998 and below the period of record for each gage (Table B4). Discharges at stream gages ranged from 1.7 to 4.4 times higher than the 7Q10 low flow estimates (USGS 1998). Data collected during this survey are interpreted as being representative of dry weather conditions.
11 August, 1998: This survey was conducted during and following relatively dry weather with only 0.15 inches of rain recorded at the Leominster gage on the sampling date(Table B2). Streamflows were generally below the monthly averages for August 1998 and below the period of record for each gage (Table B4). Discharges at stream gages were approximately two times higher than the 7Q10 low flow estimates (USGS 1998). Data collected during this survey are interpreted as being representative of dry weather conditions.
1


2 August, 1998:
Precipitation was recorded at the Leominster gage on the sample date as well as on the previous day, 1.31 inches and 0.15 inches, respectively (Table B2, Figure B5). Field crews also noted rain on these days. As detailed in Table B4 and depicted in Figure B5, a and b, the flow at the USGS gages in the North Nashua River responded to the precipitation event. The rain event appeared to be localized to the North Nashua River area because although there was an increase in flow on the Squannacook River it doesn’t appear as significant as the response at the North Nashua River gage (Figure B5, c). Discharges at stream gages were approximately four to seven times higher than the 7Q10 low flow estimates (USGS 1998). Streamflows were generally below the monthly averages for August 1998 and below the period of record for each gage (Table B4). The data are considered being representative of wet weather conditions.
9
Figure B5. Flow and precipitation data for the Nashua River Basin during the period of 8/7/98 through 8/12/98. Flow data from USGS gages. Precipitation data from Leominster station # 517.
September 1998:
This survey was conducted during and following relatively dry weather (Table B2). Streamflows were generally below the monthly averages for September 1998 and below the period of record for each gage (Table B4). Discharges at the stream gages were approximately one to two times higher than the 7Q10 estimates (USGS 1998). Data collected during this survey will be interpreted as being representative of dry weather conditions.
7 October, 1998: Although 0.80 inches of rain were recorded at the Leominster station (Table B2) on the sampling date, no precipitation was recorded for the preceding five days. Streamflows were generally below the monthly averages for October 1998 and below the period of record for each gage (Table B4). Discharges at the stream gages were approximately one to two times higher than the 7Q10 estimates (USGS 1998). Data collected during this survey will be interpreted as being representative of dry weather conditions.
Table B2. 1998 MA DEM Precipitation Data Summary (MA DEM 1998).


Nashua River Basin Survey

Precipitation Data Summary (reported in inches of rain)






















Survey Dates

5 Days Prior

4 Days Prior

3 Days Prior

2 Days Prior

1 Day Prior

Sample Date






















Kendall Reservoir Station, Holden # 423






















5/27/98

0.0

0.0

0.0

0.0

0.0

0.0

6/17/98

0.89

2.25

0.40

0.20

0.41

0.85

7/21/98

0.0

0.0

0.0

0.0

0.09

0.0

7/22/98

0.0

0.0

0.0

0.09

0.0

0.01

8/11/98

0.19

0.0

0.0

0.0

0.0

0.02

8/12/98

0.0

0.0

0.0

0.0

0.02

0.18

9/9/98

0.0

0.0

0.04

0.24

0.0

0.0

10/7/98

0.0

0.0

0.0

0.0

0.0

0.05






















EOS Leominster WWTP, Leominster # 517






















5/27/98

0.0

0.0

0.0

0.0

0.0

0.0

6/17/98

0.70

2.10

1.05

0.20

0.18

0.15

7/21/98

0.0

0.05

0.0

0.0

0.0

0.0

7/22/98

0.05

0.0

0.0

0.0

0.0

0.0

8/11/98

0.0

0.0

0.0

0.0

0.0

0.15

8/12/98

0.0

0.0

0.0

0.0

0.15

1.31

9/9/98

0.0

0.0

0.08

0.15

0.0

0.06

10/7/98

0.0

0.0

0.0

0.0

0.0

0.80


Table B3. 1998 DEP DWM Nashua River Basin stream discharge measurements.

Time Collecting Sampling Velocity Discharge

(24hr) Agency Technique (fps) (cfs)

NASHUA RIVER

Station: NM25

Description: downstream (north) off Route 2A bridge, Ayer/Shirley

05/27/98 12:10 DEP Teledyne Gurley PriceAA 0.77 349 e

07/22/98 10:45 DEP Teledyne Gurley PriceAA 0.37 146

08/12/98 9:15 DEP Teledyne Gurley PriceAA 0.27 110

09/09/98 9:40 DEP Teledyne Gurley PriceAA 0.19 74.5

10/07/98 10:22 DEP Teledyne Gurley PriceAA 0.30 114 e

NASHUA RIVER

Station: NM21

Description: downstream (north) off tank bridge (accessed from Oxbow National Wildlife Refuge off Still River Road,

Harvard), Harvard/Lancaster

07/22/98 13:30 DEP Teledyne Gurley PriceAA 0.30 92.5

08/12/98 12:00 DEP Teledyne Gurley PriceAA 0.27 78.0

09/09/98 13:00 DEP Teledyne Gurley PriceAA 0.15 39.7

10/07/98 13:30 DEP Teledyne Gurley PriceAA 0.14 36.3

e = flow estimated see field sheet for details


Table B4. 1998 USGS Flow Data Summary (Socolow et al. 1999 and 2000).


Nashua River Basin Survey

USGS Flow Data Summary (reported in cfs)

























Survey Dates

5 Days

Prior


4 Days

Prior


3 Days

Prior


2 Days

Prior


1 Day

Prior


Sample Date

Monthly Mean

POR* Monthly Mean

North Nashua River at Fitchburg, MA. (Provisional 7Q10 = 8.846 cfs (USGS 1998))

Gage #01094400






















5/27/98

89

85

78

72

67

59

194

147

6/17/98

73

282

1160

767

794

584

304

96.1

7/21/98

43

41

39

31

32

31

65.9

47.0

7/22/98

41

39

31

32

31

31

65.9

47.0

8/11/98

20

20

18

14

13

18

19.4

47.8

8/12/98

20

18

14

13

18

67

19.4

47.8

9/9/98

10

9.2

7.7

9.2

12

11

12.7

41.6

10/7/98

13

10

8.9

9.1

10

12

48.7

79.9

North Nashua River at Leominster, MA. (Provisional 7Q10 = 32.788 cfs (USGS 1998))

Gage #01094500






















5/27/98

161

148

136

128

120

108

379

246

6/17/98

123

742

2090

1420

1210

999

546

164

7/21/98

78

73

69

62

59

59

124

90.2

7/22/98

73

69

62

59

59

58

124

90.2

8/11/98

72

66

51

45

43

49

55.2

81.0

8/12/98

66

51

45

43

49

163

55.2

81.0

9/9/98

37

35

33

36

40

37

42.2

86.8

10/7/98

38

39

36

35

37

37

98.1

116

Squannacook River at West Groton, MA. (Provisional 7Q10 = 6.525 cfs (USGS 1998))

Gage #01096000






















5/27/98

95

87

78

71

65

60

196

149

6/17/98

65

189

1000

1460

712

782

330

83.3

7/21/98

43

39

37

33

30

29

63.5

37.3

7/22/98

39

37

33

30

29

29

63.5

37.3

8/11/98

18

20

20

19

17

18

23.5

29.2

8/12/98

20

20

19

17

18

29

23.5

29.2

9/9/98

14

14

13

13

14

13

13.7

30.8

10/7/98

9.5

9.8

10

11

11

11

28.1

54.4

Nashua River at East Pepperell, MA. (Provisional 7Q10 = 45.968 cfs (USGS 1998))

Gage #01096500






















5/27/98

693

570

571

510

431

415

1091

734

6/17/98

532

607

2470

3850

3950

3320

1488

492

7/21/98

263

280

261

250

247

243

427

255

7/22/98

280

261

250

247

243

187

427

255

8/11/98

82

104

296

189

112

79

170

215

8/12/98

104

296

189

112

79

136

170

215

9/9/98

118

118

117

115

162

223

122

232

10/7/98

111

133

253

246

86

225

303

318

* Period of Record
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